Fertilize now before ban goes into effect

Now that May has arrived, we are in the final month that our lawn, ornamentals and edible plants can be fertilized before the fertilizer ban goes into effect.

A trip to the local garden center can result in a confusing selection of fertilizers. Synthetic (inorganic) fertilizers come in all sorts of combinations of nitrogen, phosphorus and potassium (of course, a soil test is the only way to know for sure what nutrients need to be supplied). Too many choices can be so confusing.

Recently, I visited many garden centers to check out the types of lawn fertilizers available. The fertilizer ordinance specifies that fertilizers that contain nitrogen, must have at least 50 percent of the nitrogen be in a slow-release form. The choices of synthetic fertilizers are huge, but I could not find one organic lawn fertilizer in any of the stores that I visited.

Organic fertilizers are made from natural ingredients such as manures, dried blood, bone meal, sludge, and other plant or animal products. These fertilizers generally contain between 3 percent to 10 percent nitrogen. The benefits of using organic fertilizers are: nutrients are made available, in small amounts, on a continual basis to the plants (slowly over time) because they need to be broken down by the soil microorganisms; a food source for the soil microbes and as they consume the fertilizer, they convert the nutrients into forms that can be used by plants; they are not made of salts (as synthetic fertilizers are) so they don’t kill any soil microbes; and due to the slow-release properties of these materials, they are less apt to leach from the soil, burn plant roots, or cause rapid growth spurts.

This is very important for both the Indian River Lagoon and the St. Johns River because the use of organic fertilizers could reduce the nitrogen and phosphorus contamination of ground-water and local waterbodies.

There are some key points to keep in mind when using organic fertilizers. Because they are dependent on microbial activity, soil temperatures and pH can play a large role in plant uptake of the nutrients. The use of granular organic fertilizers during our cold months may not result in any plant response.

Of course, applying a synthetic fertilizer during the winter is also not advised because when plants are not actively growing they won’t absorb the 50 percent quick release nitrogen that is available when the fertilizer is watered in after the initial application. The use of a liquid organic fertilizer, like fish hydrolysate, is good to use during the cold months since the nutrients are already dissolved in water and can enter the roots by diffusion. Water the plants lightly with the liquid organic fertilizer so that the solution stays in the root zone, where it is needed.

Another food source for soil microbes is organic matter. Composting is a common practice of gardeners which can be done with yard waste that goes through multiple cycles of heating and cooling until humus is created. Humus, which is recognized by its brown color, earthy smell and unrecognizable ingredients, is decomposed organic matter. For those gardeners who would rather not spend a lot of effort on maintaining a compost pile, vermicomposting is also a great way to create valuable humus for the garden.

A major component of humus are humic acids and some of the sources of humic acids have been decomposing for thousands of years such as deposits of peat, lignite, coal, or marine algae. They often contain plant hormones and sometimes the addition of supplemental hormones may provide benefits; for example, the plant hormone cytokinin is often found lacking in turfgrass that has suffered a root dieback or decline. Application of cytokinin can offset the resulting stress from the root decline. Applications of humic substances can provide benefits beyond those offered by just the use of compost. In addition to supplying nutrients, increasing soil nutrient availability, and improving soil structure, humates have been shown to enhance photosynthesis, protein synthesis, root functioning and seed germination.

These are especially beneficial in soils that are low in organic matter, such as sandy Florida soils. A great way to add organic matter to the lawn is to topdress with ¼ to ½ inch of mushroom compost or compost in the spring and fall.

Another method for increasing the organic matter in the soil is to make use of cover crops. Cover crops can used as a companion plants or grown as a green manure to be cut down when young to add the organic matter and nutrients back to the soil. Overseeding the lawn in fall, with cool season annual rye grass, is an easy way to enjoy a green lawn through the winter and then when it dies in the spring, it will add more organic matter to the lawn. Another benefit of incorporating cover crops in the landscape is that they also increase biodiversity.

The more variety of plants grow above ground equals a larger variety of soil macro and microorganisms below ground.

The use of organic fertilizers, composting and/or vermicomposting, topdressing the lawn, and the use of cover crops are all great additions to our gardening practices. By feeding and nurturing the soil food web, our soil can produce organic matter, the plants are fed and protected by the soil microbes and the water quality within the watershed is protected from the leaching of excess nitrogen and phosphorus.

Sally Scalera is an urban horticulture agent and master gardener coordinator for the University of Florida’s Institute of Food and Agriculture Sciences.